1. Field of the Invention
The present invention generally relates to a method and corresponding structure that prevents insulator cracking at a corner or edge of a non-planar damascene metal wire.
2. Background
Insulator cracking at the corner or edge of non-planar damascene wire is a common problem in semiconductor fabrication where the metal wire inductor structures are relatively thick, (>3 microns), and the surrounding adjacent insulating materials, (e.g., silicon dioxide, SiO2), are relatively brittle. Since the metal inductors and corresponding insulators have a significant mismatch in their coefficient of thermal expansion, e.g., a copper (Cu) inductor may have a coefficient of thermal expansion of approximately twenty (20) times that of the coefficient of thermal expansion of a SiO2 insulator, the mismatch in coefficients of thermal expansion typically causes the more brittle insulator to crack at stress risers located on the inductor. These stress risers are usually located at corner portions of the metal inductors that occur at discrete layers of a damascene metal structure during the fabrication of the entire non-planar damascene metal inductor.
Advanced analog and mixed-signal applications require these metal inductor layers and are typically fabricated in matching networks for very high frequency applications. However, for high quality inductors with low resistive losses, the inductor thickness is typically much greater than interconnect wiring. Thus, to achieve the design requirements of low resistive losses, the metal damascene inductors are relatively large in size with respect to the surrounding insulator material, and therefore, have a higher propensity of causing cracking due to stress build-up between the two thermally-mismatched materials.